Tepexpan Palaeoindian site, Basin of Mexico: multi-proxy evidence for environmental change during the late Pleistocene–late Holocene     

Angela L. Lamb  Silvia Gonzalez  David Huddart  Sarah E. Metcalfe  Christopher H. Vane  Alistair W.G. Pike 《Quaternary Science Reviews》2009,28(19-20):2000-2016

The Tepexpan Palaeoindian skeleton was discovered in 1947 close to the former Lake Texcoco margin, in the Basin of Mexico. The find has been the object of considerable interest and discussion over the last 60 years regarding its real age and archaeological interpretation. Here we report new AMS radiocarbon dates associated with the sedimentary succession at Tepexpan with ages between 19,110 ± 90 and 612 ± 22 ¹⁴C years BP and a new uranium-series date for the skeleton with an age of 4700 ± 200 years BP that indicates a mid Holocene age. The sedimentary succession was studied in detail using: stable isotopes, diatoms, organic geochemistry and tephrochronology. The multi-proxy evidence suggests large changes around the margins of Lake Texcoco in terms of the balance between aquatic and terrestrial plants, C₃ and C₄ plants, saline, alkaline and freshwater conditions, volcanic activity, marginal reworking of lake sediments and input from the drainage basin through the late Pleistocene–late Holocene. These changes had large impacts on the prehistoric human populations living by the lake shores since the late Pleistocene in the Basin of Mexico.  相似文献   

Using Common LISP in the EAVE autonomous underwater vehicle     

Bowen  P.S. Chappell  S.G. Gonzalez  R. 《Oceanic Engineering, IEEE Journal of》1990,15(3):22w1-22w7

The Marine Systems Engineering Laboratory of the University of New Hampshire has ported the University of Utah's Portable Common LISP Subset (PLCS) to the experimental autonomous vehicle (EAVE) underwater autonomous vehicle. Using Common LISP in the EAVE autonomous vehicle is expected to improve programmer productivity and software portability. Using the LISP interpreter allows for software changes to be made while in the field, thus saving time during vehicle operations. Issues concerning the operation of LISP in a real-time environment, such as the impact of garbage collection (GC), have been resolved by using an efficient version of Common LISP and by using LISP) at the high-end of a time-based software hierarchy  相似文献   

Effect of swelling inhibitors on the swelling and stress relaxation of clay bearing stones     

Inmaculada Jimenez Gonzalez  George W. Scherer 《Environmental Geology》2004,46(3-4):364-377

Clay-containing stones such as Portland Brownstone (USA), Villarlod Molasse (Switzerland) and Tarifa Sandstone (Spain), are expected to weather as a result of wetting and drying cycles. During drying events, contraction of the drying surface leads to stresses approaching the tensile strength of the stone. However, we have found that the magnitude of these stresses is reduced by the ability of the stone to undergo stress relaxation. In this paper we describe novel methods to determine the magnitude of the stresses and the rate at which they develop and relax. We also discuss the influence of swelling inhibitors on the magnitude of swelling and the rate of the stress relaxation of these stones. The implications of our findings for the understanding of damage due to swelling of clays are discussed.Special Issue: Stone decay hazards  相似文献   

About some very small harmonics which are present in the tide of the Pacific     

Gabriel Godin  Ignacio Gonzalez 《Ocean Dynamics》1991,44(3):115-132

Summary Over 85% of the harmonic components of the tide along the west coast of Mexico have amplitudes smaller than 2 cm. Yet they are fully resolvable from the noise back-ground so that cotidal charts could be drawn for minor components such asQ ₁ andT ₂ . A cotidal chart forS ₁ ist also presented; the presence of this component is attributed not to the tidal forces but to some irregularity in the shape of the Earth or in the distribution of its mass. Third order effects of a magnitude of 1 to 9 mm are evident in the semidiurnal band; they actually exceed the second order input at some stations. The presence of compound harmonics of nonlinear origin, such as2MK ₂ ,MOK ₂ andNK ₃ is also detectable.

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Über einige sehr kleine harmonische Konstanten, die in den Gezeiten des Pazifiks vorkommen

Zusammenfassung Über 85% der harmonischen Komponenten entlang der Westküste von Mexiko haben Amplituden kleiner als 2 cm. Dennoch sind sie vollständig aus dem Hintergrundrauschen herauszufiltern, so daß für kleinere Komponenten wieQ ₁ undT ₂ Karten der Linien gleicher Amplitude und Phase gezeichnet werden können. FürS ₁ wird ebenfalls eine solche Karte dargestellt. Das Vorhandensein dieser Komponente ist nicht auf die Gezeitenkräfte zurückzuführen, sondern auf Unregelmäßigkeiten in der Gestalt der Erde oder in der Verteilung ihrer Masse. Effekte dritter Ordnung in einer Größe von 1 bis 9 mm sind offensichtlich in halbtägigen Gezeiten enthalten. Sie übersteigen sogar die der zweiten Ordnung an einigen Stationen. Das Vorhandensein von Verbundtiden nichtlinearen Ursprungs wie2MK ₂ ,MOK ₂ undNK ₃ ist ebenfalls erkennbar.

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Propos sur les très petites constantes harmoniques perceptibles dans les marées du Pacifique

Résumé Plus de 85% des composantes de la marée, le long de la côte occidentale du Mexique, ont une amplitude qui n'excède pas 2 cm. Néanmoins, elles émergent clairement du bruit de fond, ce qui permet même d'en tracer des cartes cotidales, soient celles deQ ₁ ouT ₂ par exemple. Nous présentons aussi une telle carte pourS ₁ : nous attribuons son existence non à la force de marée, mais plutôt à quelque déformité dans la géoide ou dans la distribution de sa masse. Des effets de troisième ordre, de 1 à 9 mm d'envergure, sont manifestes dans la bande semidiurne; en fait ils dépassent la contribution du deuxième ordre en certains endroits. Des composantes d'origine non linéaire, comme2MK ₂ ,MOK ₂ etNK ₃ , se descernent aussi.

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Neoproterozoic zirconium-depleted boninite and tholeiitic series rocks from Adola, southern Ethiopia   总被引：1，自引：0，他引：1  

Begashaw Wolde  Zemene Asres  Zerihun Desta  Julio J. Gonzalez 《Precambrian Research》1996,80(3-4)

In Adola, southern Ethiopia, mafic and ultramafic igneous rocks occur in narrow, 4–10 km wide, north-south-trending belts bounded by high-grade gneisses and migmatites. The mafic/ultramafic rocks are complexly deformed and metamorphosed in greenschist to lower amphibolite facies and are thought to be tectonically dismembered parts of an ophiolite complex. Preliminary geochemical and geochronological data highlight that the high-grade rocks in southern Ethiopia and northern Kenya include a significant portion of juvenile rocks that were accreted at the same time as ophiolitic rocks at 885-765 Ma. This is also the time of widespread oceanic magmatism and closure in the Arabian-Nubian Shield to the north.The Adola mafic rocks were previously described as island arc tholeiites and mid-ocean ridge basalts (MORB). New chemical analyses on the Megado belt rocks reveal the presence of boninites and related dacites interspersed with tholeiitic rocks. The Adola boninites are similar to the Cambrian boninites in western Tasmania in having relatively low Zr/Sm (≤32). Boninites with similarly low ratios have not been reported from elsewhere.The Adola tholeiites have high Ti/Zr (150–300). Mixing between tholeiite and boninite magmas may have resulted in elevated Ti/Zr (80–126) in some Adola boninites. Otherwise, Ti/Zr in the latter is low (20–40). Low Ti/Zr is characteristic of Tertiary boninites in the west Pacific. The fact that both Ti/Eu and Zr/Sm increase from the Adola and Tasmania type to the Tertiary boninites at constant Ti/Zr suggests that Ti might be an element that is also metasomatically added to the source of boninites and raises doubts about the role of amphibole in boninite petrogenesis.  相似文献   

Regional coda Q in Costa Rica, Central America     

Victor Gonzalez  Leif Persson 《Journal of Seismology》1997,1(3):269-287

Regional seismic apparent attenuation was estimated for Costa Rica, Central America, by using a time domain single scattering model of the shear wave coda decay of local earthquakes. The sensitivity of coda Q (Q_c) measurements with respect to geological differences in the crust is demonstrated in eight sub-regions with a large variety of tectonic and geologic properties. The Q_c estimations were performed for 96 selected local earthquakes recorded at 13 sites during a period of three months. In order to model the scattering as a weak process and to avoid short distance nonlinear effects, we made use of the S-wave coda data only from events within a hypocentral distance of 12 to 106 km with a lapse time between 9 and 53 s. Seismograms were also divided into groups with three different focal depths d, namely d<21 km, 21 kmc values are frequency dependent in the range 1–9 Hz, and are approximated by a least-squares fit to the power law Q_c(f) = Q₀(f/f₀)ⁿ. The estimated parameters of the power-law dependence of Q_c for the whole region, including all depths and possible wave paths, are Q₀ = 91 (± 8.4) and n = 0.72 (±0.071). Differences in the parameter of Q_c for different depths intervals are small, ranging from Q₀ = 90 (±0.7) and n = 0.70 (±0.006) for the uppermost group, with focal depths less than 21 km, to Q₀ = 97 (±0.7) and n = 0.79 (±0.005) for the deepest group with focal depths larger than 43 km. The regional differences in Q_c for the eight sub-regions are significantly larger when compared with the differences between the three focal depth groups. An attempt is made to interpret the variation of Q_c in terms of spatial variations in the geologic and tectonic properties of the crust. Other authors have found that the frequency exponent n might be larger in active tectonic areas and smaller in more stable regions. In the northern region of the Pacific coast we obtain a value of n = 0.52 (±0.011), which might indicate a lower level of tectonic activity when compared with n = 0.85 (±0.015) and 0.83 (±0.031), respectively, for the central and southern sub-regions along the Pacific coast. The latter two sub-regions are located closer to the active area near the Cocos ridge. We obtain the frequency exponent n = 0.72 (±0.052) along a major shear zone in central Costa Rica characterized by high volcanic activity and large geologic complexity. Values of n along the Panamean border are 0.62 (±0.029) in the north and 0.86 (±0.009) and 0.83 (±0.031) in two regions adjacent to the subduction zone and the Cocos Ridge, respectively.  相似文献   

Time-resolved spectroscopy of IR Gem at quiescence     

C. Lázaro  I. Gonzalez Martinez-Pais  J. E. Solheim  M. J. Arévalo 《Astrophysics and Space Science》1990,169(1-2):257-258

We present some preliminary results of a spectroscopic study of the cataclysmic system IR Gem at quiescence during two orbital periods.The spectra covered the wavelength range 4000–7000 Å. The variations with the phase in the equivalent width of the H line confirms the existence of a maximum at phase 0.5.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

The recruitment of gill-infesting copepods as a categorical predictor of size-at-age data in squid populations     

Pascual  S.; Gonzalez  A.F.; Guerra  A. 《ICES Journal of Marine Science》2005,62(4):629-633

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Present day sedimentary processes on the northern Iberian shelf     

J. M. A. Dias  J. M. Jouanneau  R. Gonzalez  M. F. Araújo  T. Drago  C. Garcia  A. Oliveira  A. Rodrigues  J. Vitorino  O. Weber 《Progress in Oceanography》2002,52(2-4)

The Galicia-Minho Shelf features two large mud patches, the Douro and the Galicia Mud patches. These are recent sediment bodies that have accumulated under a combination of conditions including: (1) abundant supplies of sediment; (2) morphological barriers that act as sediment traps; and (3) hydrographic conditions that favour the accumulation of fine sediment in these sinks. This paper describes the mechanisms controlling the deposition of the fine-grained sediment depositions and the processes that result in resuspension processes on the Galicia-Minho Shelf.Fine-grained sediments are provided from discharges from the river basins on the southern sector of the shelf, mainly the Douro and Minho rivers. Sediments are exported from river estuaries onto the shelf during episodic flood events. In contrast, most of the sediments originating from the Galician hinterland fail to contribute significantly to sedimentation on the shelf, because they are retained in the Galician Rías, which function as sediment traps.Sediments deposited on the shelf are frequently remobilized, particularly during southwesterly storms that coincide with downwelling conditions. Once in suspension the fine-grained sediments are transported northwards by the poleward flowing bottom currents and are eventually deposited on the Douro and Galicia Mud patches after a series of resuspension events. The locations of the two mud patches are strongly influenced by the shelf morphology.Fines already deposited on the mud patches are occasionally reintroduced into the system by large storm events. Some material from the Douro Mud patch and adjacent areas is re-deposited in the Galicia Mud patch. It is probable that sediments re-suspended from the Galicia Mud patch are carried off the shelf when storm events coincide with downwelling conditions.  相似文献   

Landslide databases in the Geological Surveys of Europe     

Gerardo Herrera  Rosa María Mateos  Juan Carlos García-Davalillo  Gilles Grandjean  Eleftheria Poyiadji  Raluca Maftei  Tatiana-Constantina Filipciuc  Mateja Jemec Auflič  Jernej Jež  Laszlo Podolszki  Alessandro Trigila  Carla Iadanza  Hugo Raetzo  Arben Kociu  Maria Przyłucka  Marcin Kułak  Michael Sheehy  Xavier M. Pellicer  Charise McKeown  Graham Ryan  Veronika Kopačková  Michaela Frei  Dirk Kuhn  Reginald L. Hermanns  Niki Koulermou  Colby A. Smith  Mats Engdahl  Pere Buxó  Marta Gonzalez  Claire Dashwood  Helen Reeves  Francesca Cigna  Pavel Liščák  Peter Pauditš  Vidas Mikulėnas  Vedad Demir  Margus Raha  Lídia Quental  Cvjetko Sandić  Balazs Fusi  Odd Are Jensen 《Landslides》2018,15(2):359-379

Landslides are one of the most widespread geohazards in Europe, producing significant social and economic impacts. Rapid population growth in urban areas throughout many countries in Europe and extreme climatic scenarios can considerably increase landslide risk in the near future. Variability exists between European countries in both the statutory treatment of landslide risk and the use of official assessment guidelines. This suggests that a European Landslides Directive that provides a common legal framework for dealing with landslides is necessary. With this long-term goal in mind, this work analyzes the landslide databases from the Geological Surveys of Europe focusing on their interoperability and completeness. The same landslide classification could be used for the 849,543 landslide records from the Geological Surveys, from which 36% are slides, 10% are falls, 20% are flows, 11% are complex slides, and 24% either remain unclassified or correspond to another typology. Most of them are mapped with the same symbol at a scale of 1:25,000 or greater, providing the necessary information to elaborate European-scale susceptibility maps for each landslide type. A landslide density map was produced for the available records from the Geological Surveys (LANDEN map) showing, for the first time, 210,544 km² landslide-prone areas and 23,681 administrative areas where the Geological Surveys from Europe have recorded landslides. The comparison of this map with the European landslide susceptibility map (ELSUS 1000 v1) is successful for most of the territory (69.7%) showing certain variability between countries. This comparison also permitted the identification of 0.98 Mkm² (28.9%) of landslide-susceptible areas without records from the Geological Surveys, which have been used to evaluate the landslide database completeness. The estimated completeness of the landslide databases (LDBs) from the Geological Surveys is 17%, varying between 1 and 55%. This variability is due to the different landslide strategies adopted by each country. In some of them, landslide mapping is systematic; others only record damaging landslides, whereas in others, landslide maps are only available for certain regions or local areas. Moreover, in most of the countries, LDBs from the Geological Surveys co-exist with others owned by a variety of public institutions producing LDBs at variable scales and formats. Hence, a greater coordination effort should be made by all the institutions working in landslide mapping to increase data integration and harmonization.  相似文献